The immune response to colonic antigens in the pathogenesis of experimental ulcerative colitis will be evaluated. Animals will be immunized with colon mucosal antigen and the antisera produces used to determine if there is colon specific antigens. Immunofluorescence and gel diffusion will be used to assay serum antibody and skin testing done for cell mediated immunity. In animals who produce an immune response to colonic antigens, the histologic alterations occurring in their colon will be evaluated. This will indicate whether or not an anti-colon immune response is capable of causing tissue alterations. However, other factors may be required to produce tissue damage to the colon. One of these factors to be evaluated will be local colonic trauma. In this regard actively immunized as well as passively and adoptively immunized animals will have their colon traumatized. In this manner the humoral and cellular mechanisms which participate in causing actual tissue distruction will be evaluated. In addition to in situ tissue alterations brought about by activated lymphocytes or serum antibody, the effect of these two aspects of the immune response on intestinal cells in vitro will be assessed. These studies will help determine whether or not immune parameters may participate in either the etiology or pathogenesis of ulcerative colitis.